In the automotive industry, proper vehicle quality requires measurement and adjustment of wheel alignment settings, both during manufacture and subsequently during the useful life of the vehicle. Proper positioning and alignment of vehicle wheels, and especially steerable wheels such as the front wheels of a vehicle, requires the setting of toe, camber angle, and caster angle. Toe is the angle between the vehicle's longitudinal axis and a plane through the center of the wheel/tire and affects the straight-ahead running of the vehicle as well as steering. Camber angle is the inclination of the wheel axis toward the road surface in a vertical plane and is negative when the top of the wheel is inclined toward the center of the vehicle. Caster angle is the tilt of the steering axis parallel to the direction of the vehicle centerline. A tilt toward the rear of the vehicle results in a positive caster angle. During assembly and/or repair of vehicles, it is important to measure, adjust or audit, and set the toe as well as the camber and caster angles of vehicle wheels, and especially steerable wheels, so the vehicle will drive and steer properly.
In the past, various methods have been used to measure toe and camber of vehicle wheels including direct and indirect methods. Direct measurement methods require human operators or mechanisms to place measurement tools in contact with the vehicle and are subject to placement error and wear. Indirect measurement methods, sometimes referred to as noncontact methods, typically include the viewing or sensing of the image of light projected on a tire when mounted on a vehicle and the use of a computer to calculate the tire position from such images to provide the ultimate alignment information. The prior known direct measurement methods were cumbersome, time-consuming, often labor-intensive, and less accurate than desired. Prior non-contact or indirect methods involve projecting one or two light beams at discrete locations on a tire, and receiving and processing reflected images of the light beams from the tire to reconstruct the wheel/tire plane.
Therefore, a need was determined for an apparatus and method for measuring and determining the orientation of a vehicle wheel and, more broadly, any three-dimensional object, which would allow determination of the plane of the wheel or object in a more accurate and robust manner to indicate the position of the wheel/tire with respect to the vehicle center line for purposes of setting the toe and/or camber of the wheel/tire for alignment purposes.